1. Field of the Invention
The present invention relates to decorative foliage, and, more particularly, to new and distinct varieties of fern, specifically, to a new and distinct variety of leatherleaf fern.
2. Description of Related Art
Ferns belong to the phylum Pterophyta. In the wild, the life cycle of ferns proceeds via alternating haploid and diploid generations. The asexual, diploid, sporophyte generation represents the fern plant as it is commonly known. The mature fern is comprised of a fleshy stem, or rhizome, adventitious roots and frondiform leaves. On the underside of the fertile leaves small brown areas representing sori may be produced. The sorus is comprized of groups of spore cases, or sporangia. When a spore germinates, it develops into a haploid, ephemeral sexual fern gametophyte called the prothallium, which is a small, flat, green structure having an apical notch and with a number of rhizoids growing on its underside. Also on the underside of the multistratose portion of the prothallium are the female sexual organs each being an egg containing archegonium. The male sex organ, or antheridium is commonly borne on the lower surface or near the margin of the unistratose wing. Sperm are biflagellated and motile and are released before archegonia are receptive thus creating the possibility in nature for cross-fertilization with prothallia having receptive archegonia. Unisexual prothallia are uncommon among the true ferns and self-fertilization is reported to be a common means to produce the perennial frond-bearing sporophyte. The rhizome is commonly parallel to the substrate and may be on the surface or somewhat below it. The roots originate as adventitious outgrowths from the rhizome which serve to anchor the plant and function in absorption of water and minerals.
The leatherleaf fern, Rumohra adiantiformis (Forst.f.) Ching (FIG. 1), also known as the leather fern or iron fern, has a varied taxonomic history, having been assigned previously to the genera Polystichum and Polypodium, and placed into the plant families Polypodiaceae, Aspidiaceae, and Davalliaceae. Some recent publications indicate that Rumohra represents a monotypic genus containing the single species R. adiantiformis. The genus has been placed in several families, but it is said that most evidence points to possible affinities with at least two families, the Dryopteridaceae and to a lesser extent with Davalliaceae. It is noteworthy in this regard that, although six species are claimed in Huxley's Dictionary of Gardening (1992), only the single type species is characterized and other txa mentioned appear to be assigned by indirect reference to other genera.
Accordingly, it is considered that Rumohra adiantiformis is a single botanical species with a range of variation sufficient that populations may be recognized at the level of botanical "form." For instance, Huxley refers to Rumohra adiantiformis "Cape Form," which is distinct by its fronds, which may reach as much as 1.5 m when grown in terrestrial fern mix, where warm and well drained. Other forms are generally endowed with smaller fronds, commonly not exceeding 90.times.75 cm when grown under suitable conditions. The usual forms of Rumohra adiantiformis under cultivation on slabs as specimen plants have medium-sized fronds that are reported to reach up to 60 cm long.
Variants of Rumohra adiantiformis are known to exist, but consistently and wisely employed variant cultivar names are unknown. The variant form, "Newbold's Diamond Leatherleaf Fern," represents a distinctive embodiment within the species selected for a combination of characteristics desirable for the foliage and floriculture industry.
True ferns commonly appear in the marketplace as foliage plants and also in the floral industry in arrangements. Rumohra adiantiformis was first produced for floral arrangements in Florida during the 1930s and 1940s, but major plantings were not started until the early 1950s. Since the 1950s the leatherleaf fern has been reported to have been used more frequently and is believed to be the most widely used cut foliage in commercial floral arrangements and corsages. The popularity of cut fronds of the leatherleaf fern derive from its superior keeping quality, ease of shipping, and versatile design qualities resulting from its form, texture, and color, as compared with asparagus fern, for instance. The asparagus fern is so finely divided, bushy, and pale in color, that is does not provide the substantive background for an arrangement as that created by the leatherleaf fern, because the leatherleaf fern leaves (fronds) are sturdy and glossy dark or deep green. Some growers have given names to a few selections of leatherleaf fern, but until now it is not known to have been sold by a cultivar name.
Leatherleaf fern is normally propagated commercially by rhizome divisions or clumps to ensure perpetuation of plants with desirable characteristics. It would be anticipated normally that leatherleaf fern propagated from spores would show variation from the parent as a result of genetic recombinations, and such sexually produced progeny may not be true to type. This relatively slow-growing species may require up to a full year for the sexually produced sporophyte to complete development of a mature rhizome and fully formed fronds of size suitable for market. Therefore, propagation by vegetative means is clearly the recourse of choice for the grower.
In the enormous market for foliage fillers for flower arrangements in the florist industry, a need exists for an attractive, hardy, and readily adaptable foliage. The leatherleaf fern has captured an increasing share of the market because of its well-known keeping and shipping qualities, as well as its rich color and pleasing silhouette as a background in floral arrangements. Although considerable variation exists among fronds of Rumohra adiantiformis found in the trade, no obvious attempt has been made to present a superior frond for the trade.
A clearly superior frond would have a predictable size, closely spaced pinnae, a rich green color, and a symmetrical profile for the whole blade and for each of the compound pinnae. It must be nearly complanate and rigid but not brittle, retain color for long periods, be easily packed and unpacked, withstand shipping well, and resist wilting.
Propagation must be efficient, tissue culture successful for production of predictable plants, and growing conditions easily maintained with a minimum of hand labor. Plants must grow year around for a continuous production to meet the need of the market.
A cause of loss to the grower during harvesting and shipping is breakage of pinnae or pinnules, which renders the frond unsalable. The pinnae of the currently sold varieties of leatherleaf fern are typically canted away from the plane formed by the rachis and pinnae. Because fronds are harvested and shipped atop one another, a complanate habit characteristic for a new variety to reduce breakage or damage in shipment would be desirable.
Even though one or more of these features may be found among fronds currently in the trade, none consistently realizes a full suite of optimal characteristics.